1. Technical Field
This document relates to methods and materials involved in identifying virally infected or vaccinated organisms (e.g., vertebrates and mammals). For example, this document relates to methods and material for identifying a mammal (e.g., a pig) having antibodies against a virus such as a porcine reproductive and respiratory syndrome (PRRS) virus.
2. Background Information
Organisms infected with a virus can mount an immune response against that infecting virus. Such an immune response can include the production of antibodies that bind to the virus. The presence of antibodies against a virus can indicate that the organism was exposed to that virus. For example, pigs infected with a PRRS virus can contain pig antibodies that bind PRRS virus.
PRRS is a viral disease of pigs, characterized by reproductive failure in sows (e.g., late-term abortions and stillbirths in sows) and respiratory difficulties in piglets (e.g., interstitial pneumonia in nursery pigs) (Collins et al., J. Vet. Diagn. Invest., 4:117-126 (1992) and Wensvoort et al., Vet Q., 13:121-130 (1991)). It was detected in North America in 1987 (Keffaber, Am. Assoc. Swine Pract. Newsl., 1:1-9 (1989) and Hill, Overview and History of Mystery Swine Disease (Swine Infertility and Respiratory syndrome). In: Proceedings of the Mystery Swine Disease Committee Meeting, October 6, Denver Co., pp. 29-30. Livestock Conservation Institute, Madison, Wis. (1990)) and in Europe in 1990 (Paton et al., Vet Rec., 128:617 (1991)). The causative agent is a small, enveloped positive-stranded RNA virus that is recovered primarily from alveolar macrophages and blood of infected swine. It is a member of the Arteriviridae, which includes equine arteritis virus (EAV; den Boon et al., J. Virol., 65:2910-2920 (1991)), lactate dehydrogenase elevating virus of mice (LDV; Plagemann and Moennig, Adv. Vir. Res., 41:99-192 (1992)), and simian hemorrhagic fever virus (SHFV; Godeny et al., In Proceedings of the 9th International Congress of Virology, p 22, August 8-13, Glasgow, Scotland (1993) and Plagemann, In Fields Virology, 3rd ed., pp. 1105-1120. Edited by B. N. Fields, D. M. Knipe and P. M. Howley. Philadelphia: Lippincott-Raven (1996)), in the Order Nidovirales (Cavanagh, Arch. Virol., 142:629-633 (1997)). Like other arteriviruses, PRRS virus infects predominantly macrophages and establishes a persistent infection in resident macrophages of numerous tissues (Lawson et al., Virus Res., 51:105-113 (1997) and Christopher-Hennings et al., J. Vet. Diag. Invest., 7:456-464 (1995)).